The northeast harbor of Oenum was built to be the main harbor for that side of the country. Gabbro was built to make traveling to Vandis much faster, so that ships wouldn't have to sail from Arkose all the way around Oenum. Gabbro was planned as a town that would be at least as big as Arkose, but it was only a small village when it met its demise.
Gabbro was at the east side of the desert. When the settlement was being built, there were concerns it would be too close to the cursed desert. These concerns were ignored. People came to live in Gabbro when it was village sized, before it was finished being built. Gabbro was a bustling harbor for forty days. The night after a strong windstorm, three people were found to have been cursed by the sand of the desert. By the next day, the curse had spread to more than half the village. Fortunately, the curse's will to spread itself didn't lead the cursed to go beyond the village, but the village was too dangerous for anyone to attempt to break the curse on the villagers. Then it was too late, the villagers consumed by the curse.
Gabbro was abandoned. A year after the disaster a group dared to venture into the village. The edge of the desert had spread right to the edge of the village. The wind on the east side of the desert is much stronger than near Basalt, which is why Basalt didn't meet the same fate as Gabbro. Chert, a harbor town, was built at the east shore, far from Gabbro, and an easier journey from Shale, main city of Oenum.